The present invention relates to emergency seat belt mechanisms and, more particularly, to an emergency seat belt mechanism having automatic inertia locking during an emergency condition wherein an inertia mass which accomplishes the locking mounts upon the locking pawl.
Emergency locking safety belt retractors used in vehicles for storing a safety belt thereon and for allowing unreeling of the safety belt from the retractor to permit the belt to be placed about, and thus restrain, a passenger during an emergency are known. These retractors allow the uncoiling of a safety belt at all times except during a crash or other emergency situation when the belt locks to prevent its further protraction. The locking is accomplished by an inertia-sensitive safety retractor lock which includes an inertia mass that responds to a crash or sudden deceleration of the vehicle in which it is mounted. This deceleration causes the inertia mass to actuate a locking pawl which engages ratchet teeth upon a spool that stores the safety belt.
As safety belts have been utilized for several years within vehicles of all types, the simple belt and adjustable buckle first utilized years ago has been replaced by evermore complex and intricate mechanisms. For example, the inertia mass which automatically locks the safety belt and prevents further protraction was developed after spring-loaded retraction of a safety belt was introduced. Spring retraction of a safety belt was, in turn, introduced because users became annoyed with a loose belt laying about a vehicle. Annoyance with a device leads to removal of the device. Removal of such a safety device clearly is not the desire of manufacturers of vehicles within which the device is mounted nor of government agencies that require the device. Accordingly, spring retraction was developed.
Spring retracted devices require locking at some protracted position to prevent further protraction during an emergency deceleration. First designs allowed the user of a safety belt to extend the belt to a given position wherein it was locked from further protraction. Once the user of this so-called automatic locking retractor placed the belt about his or her body, the belt had a tendency to continually retract while the latch within the seat belt mechanism prevented further protraction. The "cinching" effect became uncomfortable and contributed to a lack of use of the seat belt.
The cinching effect was eliminated through the utilization of a so called vehical sensitive retractor in which a continuously protractable seat belt which is prevented from further protraction by inertia locking during an emergency deceleration of the vehicle. During an emergency stop, an inertia mass has been used to cause the displacement of a locking pawl into a locking position against the ratchet teeth on a seat belt spool. See, for example, U.S. Letters Patent No. 2,708,966 which issued May 24, 1955 entitled Inertia-Operated Safety Equipment by R. L. Davis.
Experience has taught that it is possible for the locking pawl to engage the tip of a ratchet tooth and thus bounce back from a locking position. Several inertia devices have been proposed to eliminate this bouncing problem. See, for example, U.S. Letters Patent No. 3,889,898 which issued June 17, 1975 by A. Ziv entitled Piggyback Dual Lock Bar, assigned to the assignee of a present invention. See also U.S. Letters Patent No. 3,937,416 which issued Feb. 10, 1976, each of which are assigned to the assignee of the present invention.
These prior art seat belt systems have generally required the user to manually adjust the seat belt by protraction or other adjustment before operating the vehicle in which the user was riding. Such systems, referred to as active systems, have created some annoyance which, as in earlier prior art systems, resulted in lack of use. To overcome this problem, passive seat belt systems have been developed which require no adjustment by the user. An example of a passive seat belt system is shown in U.S. Pat. No. 4,245,856, entitled Emergency Release for Passive Seat Belt Systems by Z. Ziv which is assigned to the same assignee as the present invention.
In either a passive or active seat belt system it has been found that automatic inertia locking to prevent further protraction of the belt during an emergency can create problems if the inertia mass is not always mounted in a vertical position. Another problem is noise within the vehicle due to the high frequency vibration of the locking pawl. Further, most prior art systems designed to eliminate the bounce problem require multiple parts.